Send session events

⚠️

Preview — this feature is being built; the design below is the spec.

POST https://app.syntic.ai/v1/sessions/{session_id}/events

Send up to 20 events to a session: a new user message, the result of a function tool your code ran, or an approval decision. A message to an idle session starts a new turn; a message to a running session is queued for the next one.

For how this fits into a full workflow, see Sessions.

Headers

Header	Required	Value
`Authorization`	Yes	`Bearer <key>`: a private inference key (`sk_live_...`). See Authentication.
`syntic-beta`	Yes, while in preview	`agents-2026-11-01`. Without it the call fails with `400 beta_required`. See Versioning.
`Content-Type`	Yes	`application/json`

Path parameters

Parameter	Type	Description
`session_id`	string	The session id, starting with `sesn_`.

Body parameters

Parameter	Type	Required	Notes
`events`	array	Yes	1 to 20 events, each up to 1 MB.

Event types:

`type`	Fields	Use
`user.message`	`content`: a string or content parts	Say something to the agent.
`user.tool_result`	`tool_call_id`, `content`, optional `is_error`	Return the result of a tool whose `executor` is `client`.
`user.approval`	`tool_call_id`, `decision` (`approve` or `reject`), optional `reason`	Answer an `approval.required` event.
`user.interrupt`	none	Stop the current turn, like Interrupt a session.

Response

202 Accepted, Content-Type: application/json

{
  "data": [
    {
      "id": "evt_01JC7M4D",
      "type": "user.tool_result",
      "tool_call_id": "call_7",
      "created_at": "2026-11-05T10:00:09Z"
    }
  ]
}

Examples

curl -sS https://app.syntic.ai/v1/sessions/sesn_01JC7M2K4P6R8T0V2X4Z/events \
  -H "Authorization: Bearer $SYNTIC_API_KEY" \
  -H "syntic-beta: agents-2026-11-01" \
  -H "Content-Type: application/json" \
  -d '{
      "events": [
        {
          "type": "user.tool_result",
          "tool_call_id": "call_7",
          "content": "{\"status\": \"delivered\", \"total\": 41.20}"
        }
      ]
    }'

import os
 
import requests
 
resp = requests.post(
    "https://app.syntic.ai/v1/sessions/sesn_01JC7M2K4P6R8T0V2X4Z/events",
    headers={
        "Authorization": f"Bearer {os.environ['SYNTIC_API_KEY']}",
        "syntic-beta": "agents-2026-11-01",
    },
    json={
        "events": [
            {
                "type": "user.tool_result",
                "tool_call_id": "call_7",
                "content": "{\"status\": \"delivered\", \"total\": 41.20}",
            },
        ],
    },
    timeout=60,
)
data = resp.json()
if not resp.ok:
    raise RuntimeError(f"{resp.status_code} {data['error']['code']}: {data['error']['message']}")
print(data)

const res = await fetch('https://app.syntic.ai/v1/sessions/sesn_01JC7M2K4P6R8T0V2X4Z/events', {
  method: 'POST',
  headers: {
    Authorization: `Bearer ${process.env.SYNTIC_API_KEY}`,
    'syntic-beta': 'agents-2026-11-01',
    'Content-Type': 'application/json',
  },
  body: JSON.stringify({
    "events": [
      {
        "type": "user.tool_result",
        "tool_call_id": "call_7",
        "content": "{\"status\": \"delivered\", \"total\": 41.20}"
      }
    ]
  }),
})
const data = await res.json()
if (!res.ok) throw new Error(`${res.status} ${data.error.code}: ${data.error.message}`)
console.log(data)

package main
 
import (
	"fmt"
	"io"
	"net/http"
	"os"
	"strings"
)
 
func main() {
	body := strings.NewReader(`{
  "events": [
    {
      "type": "user.tool_result",
      "tool_call_id": "call_7",
      "content": "{\"status\": \"delivered\", \"total\": 41.20}"
    }
  ]
}`)
	req, err := http.NewRequest("POST", "https://app.syntic.ai/v1/sessions/sesn_01JC7M2K4P6R8T0V2X4Z/events", body)
	if err != nil {
		panic(err)
	}
	req.Header.Set("Authorization", "Bearer "+os.Getenv("SYNTIC_API_KEY"))
	req.Header.Set("syntic-beta", "agents-2026-11-01")
	req.Header.Set("Content-Type", "application/json")
 
	resp, err := http.DefaultClient.Do(req)
	if err != nil {
		panic(err)
	}
	defer resp.Body.Close()
 
	out, _ := io.ReadAll(resp.Body)
	if resp.StatusCode >= 300 {
		panic(fmt.Sprintf("%d: %s", resp.StatusCode, out))
	}
	fmt.Println(string(out))
}

import java.net.URI;
import java.net.http.HttpClient;
import java.net.http.HttpRequest;
import java.net.http.HttpResponse;
 
public class Example {
    public static void main(String[] args) throws Exception {
        String body = """
            {
              "events": [
                {
                  "type": "user.tool_result",
                  "tool_call_id": "call_7",
                  "content": "{\\"status\\": \\"delivered\\", \\"total\\": 41.20}"
                }
              ]
            }
            """;
        HttpRequest request = HttpRequest.newBuilder(URI.create("https://app.syntic.ai/v1/sessions/sesn_01JC7M2K4P6R8T0V2X4Z/events"))
            .header("Authorization", "Bearer " + System.getenv("SYNTIC_API_KEY"))
            .header("syntic-beta", "agents-2026-11-01")
            .header("Content-Type", "application/json")
            .method("POST", HttpRequest.BodyPublishers.ofString(body))
            .build();
        HttpResponse<String> response = HttpClient.newHttpClient()
            .send(request, HttpResponse.BodyHandlers.ofString());
        if (response.statusCode() >= 300) {
            throw new RuntimeException(response.statusCode() + ": " + response.body());
        }
        System.out.println(response.body());
    }
}

using System.Net.Http.Headers;
using System.Text;
 
using var http = new HttpClient();
using var request = new HttpRequestMessage(new HttpMethod("POST"), "https://app.syntic.ai/v1/sessions/sesn_01JC7M2K4P6R8T0V2X4Z/events");
request.Headers.Authorization = new AuthenticationHeaderValue("Bearer", Environment.GetEnvironmentVariable("SYNTIC_API_KEY"));
request.Headers.Add("syntic-beta", "agents-2026-11-01");
request.Content = new StringContent("""
    {
      "events": [
        {
          "type": "user.tool_result",
          "tool_call_id": "call_7",
          "content": "{\"status\": \"delivered\", \"total\": 41.20}"
        }
      ]
    }
    """, Encoding.UTF8, "application/json");
 
using var response = await http.SendAsync(request);
var text = await response.Content.ReadAsStringAsync();
if (!response.IsSuccessStatusCode) throw new Exception($"{(int)response.StatusCode}: {text}");
Console.WriteLine(text);

<?php
$body = <<<'JSON'
{
  "events": [
    {
      "type": "user.tool_result",
      "tool_call_id": "call_7",
      "content": "{\"status\": \"delivered\", \"total\": 41.20}"
    }
  ]
}
JSON;
 
$ch = curl_init('https://app.syntic.ai/v1/sessions/sesn_01JC7M2K4P6R8T0V2X4Z/events');
curl_setopt_array($ch, [
    CURLOPT_CUSTOMREQUEST => 'POST',
    CURLOPT_RETURNTRANSFER => true,
    CURLOPT_HTTPHEADER => [
        'Authorization: Bearer ' . getenv('SYNTIC_API_KEY'),
        'syntic-beta: agents-2026-11-01',
        'Content-Type: application/json',
    ],
    CURLOPT_POSTFIELDS => $body,
]);
$response = curl_exec($ch);
$status = curl_getinfo($ch, CURLINFO_RESPONSE_CODE);
curl_close($ch);
 
if ($status >= 300) {
    throw new RuntimeException("$status: $response");
}
print_r(json_decode($response, true));

require "json"
require "net/http"
require "uri"
 
uri = URI("https://app.syntic.ai/v1/sessions/sesn_01JC7M2K4P6R8T0V2X4Z/events")
req = Net::HTTP::Post.new(uri)
req["Authorization"] = "Bearer #{ENV.fetch('SYNTIC_API_KEY')}"
req["syntic-beta"] = "agents-2026-11-01"
req["Content-Type"] = "application/json"
req.body = <<~'JSON'
  {
    "events": [
      {
        "type": "user.tool_result",
        "tool_call_id": "call_7",
        "content": "{\"status\": \"delivered\", \"total\": 41.20}"
      }
    ]
  }
JSON
 
res = Net::HTTP.start(uri.host, uri.port, use_ssl: true) { |http| http.request(req) }
raise "#{res.code}: #{res.body}" unless res.is_a?(Net::HTTPSuccess)
puts JSON.pretty_generate(JSON.parse(res.body))

Errors

Errors use the error envelope and carry a request_id. Codes specific to this operation:

Status	`type`	`code`	When
400	`invalid_request_error`	`beta_required`	The `syntic-beta` header is missing.
404	`not_found_error`	`session_not_found`	No session with that id in this workspace.
409	`conflict_error`	`session_archived`	The session is archived.
409	`conflict_error`	`tool_call_not_pending`	No tool call with that id is waiting for a result or approval.
413	`invalid_request_error`	`event_too_large`	One event is over 1 MB.
401	`authentication_error`	`invalid_api_key`	The key is missing, unknown, revoked or expired.
429	`rate_limit_error`	`rate_limited`	Too many requests; wait for `Retry-After`. See Rate-limit headers.

Stream session events

Update a session Stream events

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